From the U.S. Preventive Services Task Force, Agency for Healthcare Research and Quality, Rockville, Maryland.

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17 Comments

Lewis ware MD

St Johns Regional Medical Center,Joplin,MO

November 17, 2009

The 40-50 age group.

As lead mammographer in my hospital, I can tell you that if we stop screening 40-50 yr. olds we will experience a giant step backward in detecting early cancer. Many of the cases that are detected at in situ or stage 1 will be seen later in her life as Stage 3 or 4 ; not much prevention there. I am sure women are much smarter than that. Shame on giving in on Government health care ideas.

Conflict of Interest:

None declared

philip s walter

No Affiliation

November 18, 2009

Re:The 40-50 age group.

This is one problem with what we do on a daily basis. Evidence has to be separated from the intuitive reactions we have. The response from the radiologist implies that he knows that all of the tumors he finds will have an impact on the life of the patient.

Conflict of Interest:

None declared

Victoria L. Seewaldt

Duke University

November 18, 2009

Re:The 40-50 age group.

The U.S. Preventive Services Task Force (USPSTF) recently recommended against routine mammographic screening in women ages 40-49 (1). The recommendation was based on the relative probability of unscreened women dying of breast cancer and the reduction in mortality provided by mammographic screening. Based on these studies the USPSTF issued a blanket recommended against routine screening mammography in all women 40-49 years -of-age (1).

Lacking from the USPSTF study is evidence to support a reduction in mammography screening in African American and Latino women who are less than 50 years-of-age (1). The USPSTF study analyzed the risk/benefit mammography as a function of a woman's age but did not consider the potential contributions of race and ethnicity (1). Investigators did not state the racial and ethnic composition of study participants and there was no analysis of the risk/benefit of mammography in African-American and Latino women (1).

It is concerning that USPSTF issued a one-size-fits-all blanket breast cancer screening recommendation without considering whether the recommendation is appropriate for all women.

Our current recommendations for mammographic screening are based on studies in European, European-Canadian and European-American women. Eight reported randomized trials studied mammography's effectiveness in the United States, Sweden, Canada, and the United Kingdom (for a review, see reference 2). These studies balance the relative contributions of mammographic density (sensitivity and specificity of mammography) and the death rate from breast cancers (2). To our knowledge, there has been no large-scale analysis of the effectiveness of mammographic screening in African-American and Latino women.

Studies of mammographic screening in women ages 40-49 are complex because younger women have a lower incidence of breast cancer, denser breast tissue (which can lower sensitivity), and, on average, faster growing, biologically aggressive cancers. Relative to European-American women, African-American women have lower breast density, faster growing cancers, and a higher likelihood of dying from breast cancer (3-5). Since the death rate from breast cancer in African-American women is higher and mammographic density is typically lower, it is likely that the benefit from mammographic screening will be higher in African-American, and perhaps Latino women, than in European-American women.

So where's the evidence to recommend against routine mammography screening of African American and Latino women under 50 years-of-age?

We agree with the USPSTF that there is a need for change. But the change we call for is an end to one-size-fits-all recommendations and inclusion of African-American and Latino women in clinical trials testing the benefit of mammographic screening.

Conflict of Interest:

None declared

The Editors

Annals of Internal Medicine

November 20, 2009

The Editors' Response

"In response to media reports that imply otherwise, Annals of Internal Medicine did not schedule the publication of the US Preventive Services Task Force recommendations about breast cancer screening to coincide with a particular date or event. The background papers (which underwent several rounds of revision over about 5 months based on independent peer review comments and Annals' statistical editor's comments) and the recommendation statement were all in final, accepted form by September 10, 2009. Annals scheduled them to appear in the next available print issue, which was the November 17th issue. Our routine print production process takes about 2 months from final acceptance to print." The Editors

Conflict of Interest:

None declared

Daniel B. Kopans

Harvard Medical School/Massachusetts General Hospital

November 20, 2009

The USPSTF Recommendations Are Not Scientifically Based - Underestimate the Benefit of Mammography and Admit That Lives Will Be Lost Unnecessarily

The US Preventive Services Task Force (USPSTF) acknowledges that mammography screening, beginning at the age of 40, significantly decreases breast cancer deaths. Their guidelines, however, ignore the science and direct measurements of benefit to limit access to screening.

1. None of the parameters of screening change abruptly at the age of 50 or any other age (1). The age of 50 is an arbitrary threshold. 2. The USPSTF correctly used the randomized, controlled trials (RCT) as scientific proof of benefit. However, since the RCT did not stratify by risk, there is no proof that screening based on risk will save lives, and no scientific support for recommending screening based on risk (2). Screening only women at high risk will miss the 75-90% of breast cancers that occur in women who are not at high risk. 3. The USPSTF chose the lowest possible reduction in breast cancer deaths (15%), unaware of the fact that the RCT underestimate benefit. Women allocated to be screened who refuse the invitation, and die of breast cancer, are still counted as having been screened (non-compliance). Women allocated to be controls whose lives are saved by mammograms that they obtain outside the trial, are still counted as unscreened controls (contamination). 4. The USPSTF recognizes a 30 % decrease in breast cancer deaths in the U.S. since 1990 but ignore it, and ignore the 40% decrease in breast cancer deaths reported in Sweden (3), predominantly due to screening, that applies to women in their forties. 5 Ignoring direct data they used a 15% reduction in deaths and estimated 1300 women needed to be screened (NTS) to save one life was a reasonable number to support recommending mammography. They would deny screening to women ages 40-49 because they estimated their NTS was 1900. In reality there is 30-40% decrease in deaths for women in their forties so, using their formula, the NTS is 950-705 for women in their forties putting them well below the threshold. 6 Most false positive mammograms are easily resolved with a few extra pictures. Most biopsies are needle biopsies. Over treatment is not the fault of mammography and should be addressed to the oncologists. 7. The Task Force admits that lives will be lost by increasing the time between screens to two years.

Before denying women access to screening, anyone advising women needs to be aware of the facts.

References

1. Kopans DB. Informed decision making: age of 50 is arbitrary and has no demonstrated influence on breast cancer screening in women. Am J Roentgenology 2005;185:177-82

Conflict of Interest:

None declared

Cicero Urban

Breast Unit HNSG and Positivo University, Curitiba, Brazil

November 22, 2009

The USPSTF Recommendations should consider quality of life for breast cancer patients

The US Preventive Services Task Force (USPSTF) acknowledges that mammography screening, beginning at the age of 40, is not indicated for lower risk patients. Their guidelines, however, ignore the fact that breast cancer screening nowadays has two aims, from our point of view as breast surgeons. The first, of course, is regarding breast cancer deaths, which was discussed and can be easily calculated. But, the second one is related to the benefits of earlier diagnosis to breast surgery. We can preserve the breast and the axilla in most of patients with their breast cancer diagnosed in screening programs. Our current index of breast conservation surgery in a well selected population of brazilian patients in Curitiba (south of Brazil) who have access to screening today, is over 60%. Most of them (about 80%) had no axillary dissection, since the sentinel node was negative. These facts are directly related to quality of life in this group of patients. So there is a strong relation between screening and more conservative surgeries. I think that we can change our current recommendations in the future only if we consider the benefits to breast cancer patients in both aims. Mortality cannot be the only tool to be considered in the future guidelines. To save lifes is important, but to preserve quality of life is our current aim too in times of sentinel node and oncoplastic surgery.

Conflict of Interest:

The USPSTF recommendation that women in the age group 40-50 not have screening mammograms comes from poor judgment about breast cancer data and clinical understanding of breast cancer. Coupling this recommendation to the recommendation that women in this age group not examine themselves clearly indicates that the panel members have limited understanding of breast cancer detection. To be sure there is no good evidence that breast self-examination lowers the risk breast cancer death. However, by limiting themselves to the impact of self-examination on mortality, they failed to address a second question raised by their recommendation that these women not have mammographic screening. Who is it that most often diagnoses breast cancer in the age group of 40-50 years? In unscreened women it is overwhelmingly the women themselves. If one follows the USPSTF recommendations that women in this age should not be screened and should not perform self-examination, how are breast cancers to be diagnosed? Certainly this will not come from annual clinical breast examination.

Conflict of Interest:

Although the Task Force breast cancer screening recommendations are meant to provide guidance to clinicians and their patients, these and many other Task Force recommendations are also released in a public health arena and because they address entire or large segments of a population may have unintended or unforeseen public health impacts. Unfortunately, the current research and communications methodologies of the Task Force seem not to take this into account.

For example, the recommendation against clinicians teaching Breast Self Examination (BSE) I assume was related to a particular form of BSE. This appears to be based on several assumptions that fail to take into account the possible impact of this recommendation. First, it assumes that most such education occurs through interactions with clinicians. While the recommendation is only to clinicians, the Task Force fails to explain how this might or might not apply to other settings or persons,for example, health educators, public health departments. Nor does the lack of specificity regarding this recommendation account for the possibility that women be taught how to be more self aware of and how to conduct self examinations of their breasts for other reasons.

In addition, the language utilized in the recommendations indicates that the only concern is for clinicians and their patients. However, the recommendations are also widely disseminated in the media to populations of women who do not have health care coverage or clinicians they interact with on a regular basis - or if they do, only in emergency situations. One could easily hypothesize that the recommendations as perceived by these populations could have the unintended effect of not only decreasing use of breast cancer detection services (including public health services) but also conveying the impression that these are not important issues for those without regular health care. Furthermore, there is little consideration about what the impact on other health behaviors may be at a time when the entire health community is trying to get people to be more aware of and take a more active role in their health and health behaviors,and to shift towards prevention and early intervention before tertiary interventions may be required. While the Task Force properly tries to address one clinical issue at a time, it operates in an arena in which clinical and public health concerns and impacts naturally intermingle, where individuals apply what they have learned about one health behavior to another. As much as it may assume otherwise, the recommendations go not only to clinicians who have patients but to many who might be patients but in reality have little regular interaction with clinicians, and to non-clinicians who regularly address the same or similar health concerns with the patients of others.

It may be an overstatement that the Task Force exemplifies the unfortunate, and I think harmful, gap between our health care/clinical and public health systems. However, the Task Force format needs to be revised so that research and data from the public health arena be factored in and that there be recognition that the recommendations also have public health connotations which must also be factored in when making and releasing clincal recommendations. Richard Yoast, PhD

Conflict of Interest:

None declared

James F. Ruiz

Woman's Hospital

November 25, 2009

Distressing Internal Inconsistencies

A primary source motivating the USPSTF to alter guidelines states that "conclusions about the optimal starting ages for screening depend more on the measure chosen for evaluating outcomes. If program benefits are measured in life-years, the measure most commonly used in cost- effectiveness analysis, then our results suggest that initiating screening at age 40 years saves more life-years... Starting annual screening at age 40 years (vs. 50 years) and continuing annually to age 69 years yields a median of 33 (range, 11 to 58) life-years gained per 1000 women screened. If the goal of a screening program is to efficiently maximize the number of life-years gained, then the preferred strategy would be to screen biennially starting at age 40 years (1)."

The USPSTF proceeds to ignore these comments to state "given that the age groups (40 to 49 years and 50 to 59 years) are adjacent, the Task Force elected to emphasize the mortality outcomes from the modeling studies." However, the USPSTF fails to describe how "adjacency" of the two age groups leads one to conclude that mortality outcomes is a better measure than life years gained. Further, the USPSTF does not counter the claim by their reference source that life years gained is "the measure most commonly used in cost-effective analysis."

Nelson's review, upon which the USPSTF relied to change their recommendations, states that "harms of mammography screening have been identified, but their magnitude and effect are difficult to measure. Mammography screening at any age is a tradeoff of a continuum of benefits and harms. The ages at which this tradeoff becomes acceptable to individuals and society are not clearly resolved by the available evidence (2)." However, the USPSTF chooses to emphasize the adverse consequences for most women and classifies harms for all age groups as "moderate."

The task force identifies false positives as the major harm in the younger age group. The task force indicates that it requires 565 more mammograms to save a life in the 40-49 year age group as compared to the 50-59 year group. Schell, et al, in evaluating the recall rate for 545,505 examinations in women aged 40-49, found that the rate is on the order of 9% which would lead to a "harm" of approximately 51 instances of additional views and/or ultrasound, 5 percutaneous biopsies under local anesthesia and the discovery of one cancer (at a rate of 3 cancers/1000 mammograms)(3). In order to conclude that the harm overshadows the life saved, the task force must find that the value of a human life is something less than the combined negative value of 616 imaging exams, 5 biopsies under local anesthesia, and the discovery of one new cancer.

In the newly passed Senate health reform bill, the USPSTF has been given a prominent role in determining what kind of care will and will not be allowed in a health care system. Under the new administration, this first effort by the USPSTF does not inspire confidence.

Conflict of Interest:

None declared

Hari H. Dayal

UNTHSC, Fortwoth TX

November 30, 2009

Cost of preventing one breast cancer death for women in their 40's

The Editor Annals of Internal Medicine

Dear Editor,

The US Preventive Service Task Force (USPSTF) revised recommendations on mammography have understandably stirred fierce debate. The research cited by USPSTF in support of their recommendation for women in their 40's seems compelling.

We assume in our calculation that the average cost of a mammogram is $250, about 1% of those screened will need a biopsy at an average cost of $1,000, and about 10% will need some other less expensive testing. If indeed 1,900 women in their 40's have to be screened annually for a decade to avert one breast cancer death, the associated cost comes to approximately $5 million.

The USPSTF revised guidelines recommend against performing mammography on women in their 40's on a population basis. However, for those in their 40's at high risk, they recommend mammography on a case by case basis in consultation with the physician.

Every penny of the $5 million will be well-spent if the one breast cancer death averted is of my 45-year old daughter with no known risk factor. That is where the debate gets personal and emotional- an area where science, data, and analyses become irrelevant. And, that is where the debate gets political, seemingly making all the science, all the data, and all the analyses irrelevant.

Somewhere, somehow, someone must find a middle ground so we as a society can make efficacious use of a viable early detection method for averting breast cancer deaths. It also behooves us as a society to look into other ways to avert breast cancer deaths, such as primary prevention using dietary modification. Perhaps the policy makers in addition to early detection can play a proactive role in prevention, providing a multi- pronged strategy to fight breast cancer mortality.

Conflict of Interest:

None declared

Vickie L Ledford

Murphy Medical Center

November 25, 2009

Re:The 40-50 age group.

I can not believe this is happening!! We have come so far with our outreach to women everywhere to encourage them and assure them that early detection was the best protection to keep from dying with breast cancer. I have been a mammographer for 15 years and I have too many memories of young women in their 40's being diagnosed with breast cancer. If these women waited to come in when they were 50 the cancer could have spread to their lymph nodes and would be more complex to treat. I don't know what these people were thinking when they came out with this recommendation. Mammographers need to continue to encourage women not to wait until their 50 to get a mammogram.

Colin B. Begg

Memorial Sloan-Kettering Cancer Center

December 3, 2009

Mammography Screening Guidelines

TO THE EDITOR: In their recent evaluation of mammography, the US Preventive Services Task Force recommends screening for breast cancer bi- annually starting at age 50 (1). The Task Force has stressed that this recommendation depends solely on the trade-off between medical benefits and harms, with no consideration of costs. Editorials in both the Wall Street Journal (2) and the New England Journal of Medicine (3), however, suggest that the recommendation was in fact motivated by cost considerations. A careful examination of the data analyses by Mandelblatt et al. (4), presented in support of the recommendations, would appear to confirm the view that costs were indeed pivotal in informing the Task Force recommendation.

The Task Force states that its recommendation involves trading off the mortality benefit of screening against medical "harms" such as provoked anxiety, the adverse consequences of false positive tests including unnecessary biopsies and treatment, and the adverse effects of "over-diagnosis". But how did they use the evidence about these effects to reach their recommendation? There are no analyses in the report nor in the supporting articles (4,5) that simultaneously consider both benefits and harms and that lead directly to the specific recommendation to begin screening at age 50, and to do it bi-annually. The only analysis provided that aligns clearly with the Task Force recommendation is the analysis displayed in the Figure in Mandelblatt et al. (4) This Figure presents the results from independent analyses by six investigative groups of the projected mortality reduction for a range of screening strategies, covering various starting ages, and including options to screen annually or bi-annually. The critical feature of these analyses is that the population mortality benefit is contrasted solely with the numbers of mammograms required, a surrogate for resource utilization, and thus for costs. The authors do not utilize "harms". These analyses search for an optimal strategy at the point where the graphs plateau, representing a point of diminishing returns from additional screening. Bi-annual screening strategies starting at age 50 are close to the "optimal" inflection point in all 6 of these analyses, and this would appear to be the crucial finding that motivated the Task Force recommendation. The number of mammograms in these analyses does not represent "harm". Rather, it is a measure of the societal investment in mammography, i.e. the societal cost. In other words, this is, in effect, a thinly disguised assessment of cost relative to effectiveness, something most experts would label a cost-effectiveness analysis.

Two recent U.S. Preventive Services Task Force (USPSTF) statements on screening for breast cancer identify harms of false-positive mammography screening test results, including psychological distress (1,2). Unfortunately, the reports drift away from published evidence about psychological distress from false-positive mammograms. The summary report dismisses the problem: "Anxiety, distress, and other psychosocial effects can exist with abnormal mammography results but fortunately are usually transient (1)." We believe this statement mischaracterizes the empirical literature, and indeed what the USPSTF reports to an extent in its own detailed concurrent report (2), which more correctly states that "False-positive mammography results had no consistent effect on most women's general anxiety and depression but increased breast cancer specific distress, anxiety, apprehension, and perceived breast cancer risk for some (2)." This statement is consistent with our own recent research where we found that false-positive mammography results cause small but reliable elevations in breast cancer-specific distress (3).

The USPSTF summary also comes to a different conclusion about transience of the effects of false-positive mammograms (1,2) than two previous systematic reviews (4,5). Brett et al. state that "women who have further investigations following their routine mammogram experience significant anxiety in the short-term, and possibly in the long-term (4)." Brett et al. did not emphasize the transience of false-positive's effects as a general finding. Similarly, our own systematic review concluded that the effects of false-positive mammography results endure over the long-term, well after cancer has been ruled out (5). We believe the correct conclusion is that false-positive mammography results cause small but reliable distress that endures for months and years.

Conflict of Interest:

None declared

Mitchell H. Gail

Division of Cancer Epidemiology and Genetics, National Cancer Institute

December 16, 2009

Risk Models for Breast Cancer Screening of Women in Their Forties

The U.S. Preventive Services Task Force recommended "against routine screening mammography in women aged 40 to 49 years," writing that the decision should be based on "patient context, including the patient's values regarding specific benefits and harms." These criteria do not explicitly include risk assessment. Indeed, the report (1) seems to dismiss risk assessment based on "demographic, physical or historical risk factors for breast cancer", stating that "none conveys clinically important absolute increased risk for cancer."

Although age is the most important risk factor over long age intervals, it is not as important as other risk factors over the age range 40 to 50 years. In 1998, Gail and Rimer (2) suggested that a woman in her forties should consider mammographic screening if her absolute risk was as great as that of a fifty year old women without other risk factors, because benefits are thought to outweigh risks for such a fifty year old woman, and, as argued in (2), the same should be true for a younger woman with comparable risk. The ratio of incidence rates of a fifty year old white woman with no risk factors to a forty year old white women with no risk factors is 2.46 (2). If the forty year old has risk factors that increase her risk at least 2.46 times above baseline, she has at least the absolute risk of the fifty year old. Many risk factors, such as two affected first-degree relatives, atypical hyperplasia, and at least 75% dense tissue on a mammogram have relative risks that exceed 2.46, as do many combinations of weaker risk factors (2, 3). For a 48 year old woman, risk factors need to increase baseline risk by only 6% to put her at the risk of a 50 year old with no risk factors (2).

Recent data (1) that screening reduces breast cancer mortality by 15% in women aged 39-49 and by 14% in women aged 50-59 only strengthen arguments (2) that a woman in the age range 40-49 years with the same absolute risk as a fifty year old woman has a similar ratio of benefits to adverse effects, such as false positive results requiring further evaluation. Thus, risk factors in addition to age should be considered when counseling a woman in her forties whether or not to have screening mammograms. Of course, "the patient's values regarding specific benefits and harms" should also be considered, as recommended by the Task Force (1).

Conflict of Interest:

None declared

Peter B. Dean

University of Turku Faculty of Medicine and Turku University Hospital, Turku, Finland

December 18, 2009

Mammography Screening Guidelines Should Reflect Reliable Data

The data search for published evidence from the RCTs used by the USPSTF ended in December 2008. In June 2009 Holmberg et al. (1) published a review of the data from the Swedish Two-County Trial, which showed that the methodology used in the previous overview (2) "resulted in a reduction of the estimate of the effect of screening." Data from this previous overview (2) were used for both the 2002 and 2009 USPSTF evaluations. Although this latest Swedish overview (1) did not present results specific to age categories, the material is available for such an analysis. It is unfortunate that none of the members of the USPSTF were aware of these recently revealed flaws in their database at the time when they were in the lengthy process of deciding that the benefits of mammography screening were less than previously calculated. A more concerted effort to communicate with individuals currently working with breast cancer screening could easily have brought this newer information to their attention.

The USPSTF evaluation (3) and supporting articles are plagued with ambiguity over the use of the terms "screen" and "screening" when used alone or in conjunction with the term "mammography." Whereas the evidence of benefit has been drawn exclusively from "intention to treat" publications, the numerical conclusions have been directly applied by the USPSTF to the case of the individual woman seeking advice from her physician. If the USPSTF evaluation is taken at face value, women will be told the estimated benefit of receiving an invitation to participate in a mammography screening program, a benefit considerably lower, by a factor of approximately 1.4, than the benefit of her actually getting mammograms (4).

The harms, on the contrary, are not calculated on an "intention to basis," so the USPSTF has introduced a considerable bias into their benefit/risk calculations.

The USPSTF purports to determine, in its own words,"benefits...potential harms...and limitations of the test"(3)." The additional benefits of actually getting a mammogram have been measured in Sweden using the ongoing service screening programs (5), and results specific for women aged 40-49 have been submitted for publication. It does not appear to make good sense for the USPSTF to intentionally ignore such publications when attempting to answer their own question, since the analysis of benefit is jeopardized by exclusive reliance upon historic RCT data that were designed to answer a different question.

Conflict of Interest:

None declared

Anita Ho

Centre for Applied Ethics, University of British Columbia

January 10, 2010

The Social Context and Values Behind the Breast Cancer Screening Controversy

Regarded by many medical professionals as a premier source of information on preventive services (1), the US Preventive Services Task Force (USPSTF) was blind-sided by the recent controversy regarding its recommendation against routine screening mammography for asymptomatic women under the age of 50 (2). While the evidence-based panel prides itself on being independent of advocacy groups or managed care organizations, the controversy can be better understood if we consider the socio-political context of women's health and health-care reform. Historically, women have significantly less access to some of the major diagnostic and therapeutic interventions compared to men (3), are more likely to delay or go without necessary medical care, and express more concerns about the quality of health care they receive (4). The panel's recommendations may have prompted many to perceive, rightly or wrongly, the guidelines to be a setback in promotion of women's health.

In the midst of health-care reform discussions, the public's response may also reflect its scepticism of scientists' claim of value neutrality in evidence-based medicine and their social authority based therein. After all, even if scientific evidence is the most important factor in the panel's recommendation, what conditions are considered to create a large enough burden of suffering for society to warrant the USPSTF's investigation is partly a value judgment (5). As the USPSTF's ratings influence insurance coverage of various preventive services, the public's flat-out rejection of the panel's conclusion may be a result of its distrust in the social authority of expert opinion, confusion about the panel's decision-making process, and concerns about how rationing and funding priorities are determined by these experts.

In responding to accusations that their recommendations were politically and economically driven, the Task Force adamantly denied any financial considerations. Instead of convincing the public of its neutral stance, the USPSTF may have inadvertently perpetuated the impression that financial considerations in health care are always illegitimate. As the country continues its debate on health-care reform, the Task Force and government officials may want to use this controversy as a new opportunity to facilitate more informed and responsible discussions among citizens regarding health-care program planning and funding. Rather than simply denying that economic or social context plays any role in scientific review, it may be more fruitful for the panel to clearly explain what values were part of the consideration, and furthermore, how such values were chosen, and why such values were appropriate in determining their guidelines.

Acknowledgment

I would like to thank Dave Unger, MD, and Suze Berkhout, PhD(c), for their critical and constructive comments on an earlier draft.

References

1. Eisenberg JM, Kamerow DB. The Agency for Healthcare Research and Quality and the U.S. Preventive Services Task Force: Public support for translating evidence into prevention practice and policy. Am J Prev Med 2001;20(3S)1-2.

Conflict of Interest:

Center for Cancer Control and Information Services, National Cancer Center

July 16, 2010

Screening for breast cancer: following the analysis conducted by the U.S. Preventive Services Task Force

Background

In 2009, the U.S. Preventive Services Task Force (USPSTF) recommended that the decision to start regular screening mammography (SC. MMG) before the age of 50 years should be an individual one and take patient context into account, including the patient's values regarding specific benefits and harms (1, 2). As a metric, they calculated the number needed to invite (NNI) to screening to prevent 1 death from breast cancer by a meta-analysis of several trials previously published (3). They concluded that the net benefit is smaller for women aged 40 to 49 years with a larger NNI compared to the value for women aged 50-59. However, they did not consider different follow-up periods when comparing NNI by age group. For women aged 40 to 49 years, the average follow-up varied from 10.7 to 16.8 years in 8 trials included in the meta-analysis, while follow-up varied from 12.9 to 18.1 years for women aged 50-59 years in 5 trials and from 14.3 to 15.5 years for women aged 60-69 years in 2 trials. Shorter follow-up periods for women aged 40-49 will lead to lower cumulative mortality, which results in an overestimation of NNI.

Objective

We aimed to estimate NNI adjusted by the follow-up period in each available study in order to compare NNI between different age groups.

Methods and Findings We estimated the NNI by applying similar methods and including similar studies to those used in the USPSTF (3). A meta-analysis of mammography trials was conducted to estimate the pooled relative risk (RR) from a random-effect model under a Bayesian analysis using the WinBUGS package (4). We included 8, 5, 2 and 1 trials for women aged 40-49, 50-59, 60-69 and 70-74 years, respectively. The NNI for screening to prevent 1 death from breast cancer reported by USPSTF was defined as the inverse of the absolute risk reduction. Here, the risk was the mortality rate during the follow-up period (death/person). In taking into account the follow-up period of studies, the estimates of NNI were calculated using the mortality rate per year (death/person-year). The estimated NNI was that based on a one-year follow-up. Thus, when we compared the NNI on the assumption that the follow-up period was x years, the estimated NNI was divided by x. In this study we tried to estimate the NNIs on the assumption of 10-year, 15-year and 20-year follow-up period.

The pooled RRs and NNIs for reducing breast cancer mortality in the USPSTF report, and our estimates calculated using the same condition are shown in Table 1. Pooled RRs with adjustment for the follow-up period were similar for all age groups. On the contrary, the NNIs were different depending on the assumed follow-up periods, i.e. 10-years, 15-years, and 20-years. On the assumption of a 10-year follow-up, the NNIs for women aged 40-49 and 50-59 were estimated to be 2399 (CI, 1195 to 8550) and 1708 (CI, 452 to 10215), respectively. The longer the assumed follow-up period, the smaller the estimates of NNIs for all age groups. More importantly, the differences in NNIs between women aged 40-49 and 50-59 were smaller in our analysis than those from the USPSTF report.

Discussion

When comparing NNIs, the follow-up period directly affects the results. The NNIs are necessarily greater in shorter follow-up period, which means the NNI can be overestimated for younger age group with relatively shorter follow-up periods if not adjusted for the follow-up. The recommendations for mammography screening by USPSTF stated that an NNI of 1904 for women aged 40-49 years was too high, yet an NNI of 1339 for women aged 50-59 years was adequate (2). However, when we adjusted for the follow-up period of the trials, the estimated NNIs for women aged 40-49 were 1599 with a 15-year follow-up and 1199 with a 20-year follow-up. Whatever the conclusion, it should not be based on biased estimates of NNIs for reducing breast cancer mortality by age group.